1. Field of the Invention
The present invention relates to a switching power supply apparatus including a converter.
2. Description of the Related Art
In a switching power supply including a converter, the voltage and current of the converter are measured for the detection of an abnormality or an operating state. An error or deviation in an output voltage caused by variations in resistance of wiring and a reference voltage is stored in a storage device at the time of factory shipment for the purpose of correcting such an error or deviation.
For example, Japanese Unexamined Patent Application Publication No. 2013-78203 discloses a power supply failure detection circuit that detects the abnormality of a power supply formed of a DC-DC converter and prevents the output of an input voltage directly to the side of a load at the time of detection of abnormality. As disclosed in Japanese Unexamined Patent Application Publication No. 2013-78203, a sign of failure of a switching element is detected on the basis of an input current flowing into the switching element connected in series to an output line to the side of the load and a voltage across the switching element. Japanese Unexamined Patent Application Publication No. 2009-100496 discloses a power supply device that stores in an EEPROM a threshold value calculated on the basis of the voltage of a load detected at the time of factory shipment and compares the threshold value with the voltage of a load to detect an abnormality on the side of the load with high accuracy.
However, a measurement terminal for externally measuring a voltage is not usually provided in the middle of a circuit. It is therefore not possible to directly measure a voltage across a switching element and correct a voltage value as disclosed in Japanese Unexamined Patent Application Publication No. 2013-78203. In order to detect a voltage across the switching element and correct a voltage value, it is necessary to additionally provide a detection terminal. In this case, the number of components is increased. This leads to an increase in the size of an apparatus.
The voltage of a load measured at the time of factory shipment is obtained as a value by measurement with high accuracy. Even in a case where the correction method disclosed in Japanese Unexamined Patent Application Publication No. 2009-100496 is used, a measurement terminal for externally measuring a voltage is therefore needed in the middle of a circuit.